This is part of an investigator initiated multicenter cooperative study to gain some understanding of the pathogenesis of atherosclerosis. Autopsies on young individuals, 15 to 34, dying suddenly from accidental causes will be performed so that samples of the cardiovascular system can be studied using a standardized protocol. Morphometric and biochemical analysis will be performed on specified samples of coronary artery and aorta and will be carried out at designated core laboratories. Sepcific histologic preparation will be performed at the University of Chicago, morphometry at Ohio State, and lipid biochemistry at New Orleans. The statistical aspects of the common protocol portions of the study will be conducted by the core's statistical and data analysis laboratory in San Antonio. The specific studies to be carried out at this institution will be directed at determining the distribution of immunocytochemical markers of smooth muscle cell differentiation and leukocyte subpopulations along the length of the left anterior descending coronary artery, and the distribution of these markers with development of atherosclerotic lesions. A three-dimensional reconstruction of the distribution of the markers as well as intimal and medial volumes will be done by the morphometry laboratory at Ohio State.